Whether it's a $10 budget sunscreen or $50 high-end lotion, knowing which offers the best protection can be tricky with all the words and labels, but a Consumer NZ database with about 150 products may be able to break all down.

The refreshed data, released on Saturday, includes prices, SPF claims, water resistance claims, ingredients, where the sunscreen was made, and where and when it last had a test to check its SPF claim stacks up.

Traditionally, the consumer protection organisation used to test sunscreens, but this stopped after the introduction of the Sunscreen (Product Safety Standard) Act 2021, which requires sunscreens to be independently tested for safety and efficiency, specifically around their SPF protection claims.

Several manufacturers, including Beiersdorf (Nivea), Edgewell Personal Care (Banana Boat and Hawaiian Tropic) and Neutrogena declined to provide information to Consumer NZ, but some of their widely available sunscreens have been included in the database, excluding where and when they were testing as that data was not available.

How important is it to use sunscreen?

The skin remembers built-up damage from sun exposure so it is important to start ultraviolet (UV) radiation protection young and to keep it up as you get older, when your immune system is more vulnerable, dermatologist Amanda Oakley said.

"Skin cancers are very prevalent and the population is ageing, and as most skin cancers occur over the age of 65 and now 65 year olds are regularly living until 95, and the epidemic of skin cancer has become horrendous, especially in white-skinned people [who are at more risk]," Oakley said.

"You can go outside for just a few minutes when you're older and think 'that's all right, I didn't get burnt'. But what's happened is the long wave ultraviolet has increased that immune suppressant effect of age. And you might have got a dormant skin cancer and then it sprouts because of just those few minutes outdoors and your age."

Don't let any dip in temperatures or clouds fool you - UV radiation is about the angle of the sun. You can find the UV index on the MetService app.

"Between the hours of say 10am and 4pm, there's enough ultraviolet to damage our skin all year round, but especially from October through 'til April."

File photo.

Melanoma NZ says most skin cancers are caused by exposure to UV radiation and New Zealand has one of the highest rates of melanoma in the world.

What are the two main types of sunscreen?

There are two general groups of active ingredients in sunscreens - physical (sometimes called mineral) and chemical.

Consumer NZ's Belinda Castles said the physical sunscreens contain zinc oxide and/or titanium dioxide minerals which create a barrier to reflect UV radiation away from your skin, but it is now believed they can also absorb UV radiation, like chemical sunscreens.

Chemical sunscreens work by penetrating into the skin, absorbing UV rays and converting them into heat and releasing it from your body.

But there's no difference that we know of in terms of efficacy between these two types, Castles said.

"We do have concerns that there's no regular testing requirement, so a sunscreen might have been tested several years ago, but at least they've been tested at some stage to show that they meet their claims."

So are more expensive sunscreens worth it?

Your choice of sunscreen goes back to whether you will actually use it or not, Oakley said.

"The cost might be more of a marketing ploy [rather] than an effectiveness of the product ... but it may be more expensive to produce something that people find cosmetically acceptable.

"There are products which are thicker and thinner and stickier. They might resist water better. They might stay where they are better. But the main thing is you have to like it enough to be prepared to use it."

In addition, Consumer NZ's research of sunscreens did not find evidence of difference in protection between cheaper and more expensive ones, Castles said.

"So often it comes down to the feel of a sunscreen, the brand name, just like anything, the marketing of more expensive products."

So what should I look out for when buying a sunscreen?

Three main things to look for are 'broad spectrum' to protect against both UVA and UVB rays, consider the SPF number (30 or higher offers high or very high protection), and whether you need a water-resistant one if you are going in the water.

Oakley also recommended a smaller packet, which gives you a chance to test out whether you will like putting it on, and will still last you through summer without expiring before you have used it up.

And Melanoma NZ said SPF in your make-up is not liberal enough for effective protection.

How much should I apply and when?

The effectiveness of protection may be less about what you buy and more about how you use it. Castles says it is important to be liberal in applying it, with adults recommended to apply seven to nine teaspoons for their whole body and face.

"So the recommendation is to apply at least 20 minutes before you go outside to give it time to absorb into your skin and also reapplying it often so that every two hours you're outside. And also after swimming, or if you've been sweating a lot with exercise."

Studies show people apply only about 20 percent of what they should to adhere to guidelines, Oakley said.

"And in fact, the first time you put it on in the day, you should put two layers on to make sure you didn't miss anywhere."

Finally, it is not enough to just rely on sunscreens for protection, Castles says. Put on suitable clothing when you are going for a swim, a broad-brimmed hat, sunglasses, and seek shade when the UV index climbs or plan your activities around those times.

"Sunscreens wash off, sweat off, rub off and it's terribly expensive for reapplying sunscreen over and over again," Oakley said.

"Whereas if you buy a garment that might be expensive the first time, [but] it can be used many times."

This article provides general information. For individual health advice, speak to your GP or a qualified professional.

RNZ